Аритметичните оператори приемат числови стойности като техен операнд и връща единична числова стойност. Стандартните аритметични оператори са събиране (+), изваждане (-), умножение (*), делене(/)
Операторът за събиране произвежда сумата от числови операнди или конкатенация на стрингове.
Operator: x + y
// Number + Number -> събиране 1 + 2 // 3 // Boolean + Number -> събиране true + 1 // 2 // Boolean + Boolean -> събиране false + false // 0 // Number + String -> конкатенация 5 + 'foo' // "5foo" // String + Boolean -> конкатенация 'foo' + false // "foofalse" // String + String -> конкатенация 'foo' + 'bar' // "foobar"
The subtraction operator subtracts the two operands, producing their difference.
Operator: x - y
5 - 3 // 2 3 - 5 // -2 'foo' - 3 // NaN
The division operator produces the quotient of its operands where the left operand is the dividend and the right operand is the divisor.
Operator: x / y
1 / 2 // returns 0.5 in JavaScript (In Java, returns 0; both are integers) // (neither 1 nor 2 is explicitly a floating point number) Math.floor(3 / 2) // returns 1 1.0 / 2.0 // returns 0.5 in both JavaScript and Java 2.0 / 0 // returns Infinity 2.0 / 0.0 // ditto, because 0.0 === 0 2.0 / -0.0 // returns -Infinity
The multiplication operator produces the product of the operands.
Operator: x * y
2 * 2 // 4 -2 * 2 // -4 Infinity * 0 // NaN Infinity * Infinity // Infinity 'foo' * 2 // NaN
The remainder operator returns the remainder left over when one operand is divided by a second operand. It always takes the sign of the dividend.
Operator: var1 % var2
12 % 5 // 2 -12 % 5 // -2 -1 % 2 // -1 1 % -2 // 1 NaN % 2 // NaN 1 % 2 // 1 2 % 3 // 2 -4 % 2 // -0 5.5 % 2 // 1.5
The exponentiation operator returns the result of raising the first operand to the power of the second operand. That is, var1var2, in the preceding statement, where var1 and var2 are variables. The exponentiation operator is right-associative. a ** b ** c is equal to a ** (b ** c).
Operator: var1 ** var2
In most languages, such as PHP, Python, and others that have an exponentiation operator (**), the exponentiation operator is defined to have a higher precedence than unary operators, such as unary + and unary -, but there are a few exceptions. For example, in Bash, the ** operator is defined to have a lower precedence than unary operators.
In JavaScript, it is impossible to write an ambiguous exponentiation expression; that is, you cannot put a unary operator (+/-/~/!/delete/void/typeof) immediately before the base number.
-2 ** 2; // 4 in Bash, -4 in other languages. // This is invalid in JavaScript, as the operation is ambiguous. -(2 ** 2); // -4 in JavaScript and the author's intention is unambiguous.
2 ** 3 // 8 3 ** 2 // 9 3 ** 2.5 // 15.588457268119896 10 ** -1 // 0.1 NaN ** 2 // NaN 2 ** 3 ** 2 // 512 2 ** (3 ** 2) // 512 (2 ** 3) ** 2 // 64
To invert the sign of the result of an exponentiation expression:
-(2 ** 2) // -4
To force the base of an exponentiation expression to be a negative number:
(-2) ** 2 // 4
Note: JavaScript also has a bitwise operator ^ (logical XOR). ** and ^ are different (for example : 2 ** 3 === 8 when 2 ^ 3 === 1.)
The increment operator increments (adds one to) its operand and returns a value.
x++), then it increments and returns the value before incrementing.++x), then it increments and returns the value after incrementing.Operator: x++ or ++x
// Postfix var x = 3; y = x++; // y = 3, x = 4 // Prefix var a = 2; b = ++a; // a = 3, b = 3
The decrement operator decrements (subtracts one from) its operand and returns a value.
x--), then it decrements and returns the value before decrementing.--x), then it decrements and returns the value after decrementing.Operator: x-- or --x
// Postfix var x = 3; y = x--; // y = 3, x = 2 // Prefix var a = 2; b = --a; // a = 1, b = 1
The unary negation operator precedes its operand and negates it.
Operator: -x
var x = 3; y = -x; // y = -3, x = 3 // Unary negation operator can convert non-numbers into a number var x = "4"; y = -x; // y = -4
The unary plus operator precedes its operand and evaluates to its operand but attempts to convert it into a number, if it isn't already. Although unary negation (-) also can convert non-numbers, unary plus is the fastest and preferred way of converting something into a number, because it does not perform any other operations on the number. It can convert string representations of integers and floats, as well as the non-string values true, false, and null. Integers in both decimal and hexadecimal (0x-prefixed) formats are supported. Negative numbers are supported (though not for hex). If it cannot parse a particular value, it will evaluate to {{jsxref("NaN")}}.
Operator: +x
+3 // 3
+'3' // 3
+true // 1
+false // 0
+null // 0
+function(val){ return val } // NaN
| Specification |
|---|
| {{SpecName('ESDraft', '#sec-additive-operators', 'Additive operators')}} |
| {{SpecName('ESDraft', '#sec-postfix-expressions', 'Postfix expressions')}} |
| {{SpecName('ESDraft', '#sec-11.5', 'Multiplicative operators')}} |
| {{SpecName('ESDraft', '#sec-11.4', 'Unary operator')}} |
{{Compat("javascript.operators.arithmetic")}}